Always at your side
    FAHRENHEIT chillers run efficiently and hassle-free – and your path from first contact to operation should be no different. We help you decide whether adsorption cooling is right for you, plan and calculate the optimum system for you, advise you in obtaining public subsidies, and support you in operating your cooling system.



Competent support right from the start
How can you benefit from adsorption cooling? Which heat source is most suitable in your case? How should the overall system be designed to achieve optimal cooling results and economic benefits? How can the system be perfectly integrated into your environment? Together with engineers, planners and architects, our experts develop an individual cooling solution that perfectly suits your requirements.

Our objective is always: The best possible result in terms of efficiency, cost-effectiveness, and environmental friendliness.


We will define the most economical setup for your new cooling system.

Business case

Calculate a detailed business case using our industry leading simulation tool AdCalc

Public subsidies

We will advise you on profiting from public subsidies.

Technical design

Develop CAD drawings, including 3D animations and data exchange.


Make use of public subsidies

We are here to help you.

In several countries, the government promotes heat use and energy-efficient cooling – and in most cases, FAHRENHEIT’s climate-friendly adsorption refrigeration chillers are eligible. Often, subsidies are also available for peripherals, and for installation services. These subsidies can reach up to 50 % of the total investment.

As is so often the case with public applications, the process needs to be navigated a little. We are happy to advise you on the most appropriate funding programs, and to guide you through the application. For some of the most well-known programs, such as BAFA in Germany, we have automated tools that make the application process as easy as copying some numbers into an online form.


FAHRENHEIT cooling solutions are extremely low-maintenance. However, certain aspects, such as the vacuum in the adsorption modules, need to be checked from time to time. Together with a worldwide partner network, our service team takes care of this for you. We are at the ready for you, quickly and reliably.

Maintenance Contracts

The all-round carefree package: As part of an individual maintenance contract, we ensure the smooth operation of your system, so that you can concentrate fully on your core tasks.



Adsorption describes the accumulation of substances (gases or liquids) on the surface of a solid which commonly is known as sorbent. In adsorption chiller systems, this process is designed for cold generation using water/zeolite or water/silica gel as the pairs of working material.

Fahrenheit adsorption chillers use two different types of adsorbents, silica gel, and zeolite. Silica gel, which is known for example as a desiccant for electronic devices, is completely non-toxic and ecologically harmless. Zeolite is an environmentally friendly crystalline mineral which presents an innovative alternative for adsorption, especially when utilized via Fahrenheit’s patented zeolite coating process to achieve higher capacities.

Since adsorption is a finite process, regeneration (desorption) is required to repeat the cycle. Desorption causes the adsorbed water vapor to be released via the supplied heat.

Zeolites are a group of substances of crystalline aluminosilicates. They are environmentally friendly, harmless materials with ideal properties for adsorption. Fahrenheit developed a process called PST – Partial Support Transformation in order to optimally apply the zeolite to the heat exchanger. This process, via sophisticated chemistry, makes zeolite crystals grow directly out of the surface of the heat exchangers. This alleviates the need for any kind of coating or glue and optimizes heat conductivity. Because zeolite can reach even the smallest cavities of porous or fibrous material, the surface-to-volume ratio and therefore power density can be maximized.

Additionally, the zeolite layer forms very effective protection against corrosion. Without adhesives or glue in between the crystal and the heat exchanger, heat conductivity is maximized.

Based on our innovations in material science and design, we can achieve a significant reduction in the size of the adsorption modules for a given cooling power. Therefore weight, size, and cost can be improved simultaneously.

In adsorption cooling technology, when extreme operating conditions are encountered, zeolite is often the adsorbent of choice.

Like zeolite, silica gel is an environmentally friendly, harmless material with properties that are very suitable for adsorption. It is commonly used in dehumidification applications and has proved itself in the adsorption field.

As an adsorbent, silica gel covers a very wide and flexible drive temperature range that is suitable for many applications.

As opposed to absorption refrigeration technology, where only liquid working materials are used or recirculated, the Fahrenheit adsorption systems are based on the principle of solid sorption (adsorption). Here, a solid working material (silica gel/zeolite) is not constantly, but cyclically in contact with the evaporating refrigerant (desorption and adsorption alternate). By combining two modules, a quasi-continuous operation can be achieved.

This is characterized by periodic slight temperature fluctuations, which can be smoothed by appropriate buffers. By combining two modules, a quasi-continuous operation can be achieved.

The main advantage of the adsorber is that no pumping of liquids is necessary and there are no moving parts. Adsorption chillers have a simple and compact design.

In addition, low drive temperatures are a decisive difference. In contrast to absorption chillers, our adsorption chillers already perform well at temperatures starting from 50 °C. As a result, the sometimes lower COP, i.e. thermal efficiency, can be compensated for.

Cooling occurs quasi-continuously, resulting in periodic, short-term temperature fluctuations of up to 5K. These fluctuations can be smoothed by appropriate buffers. In general, however, these temperature fluctuations are hardly noticeable due to the inertia of the cooled thermal mass and have no practical relevance for the climate in a room.

The refrigerant used is specially treated water. In contrast to other refrigerants, water as a natural substance is completely non-toxic and ecologically harmless. For our stationary systems, the preset frost protection automatically shuts down the machine when the chilled water temperature is below 4 ° C. For the eCoo / Zeo products, the nominal temperature range for the cold water circuit is 8 to 21 ° C.

Basically, our individual AdKM performances range between 16 and 100 kW. The machines can also be interconnected (cascaded), allowing virtually unlimited cooling capacities. For larger refrigeration capacity requirements, we create customized solutions that take into account the individual requirements (eg installation area, connection options, etc.).
In principle, the machines can be set up outdoors, but this is not recommended. When installing outdoors, make sure that the system technology is roofed over, ie. H. protected against rain, snow and frost. Also, the hydraulics must be protected against freezing in case of frost. The freezing of the process water in the refrigeration unit, however, is generally harmless.

Yes. All chillers can be used both as a cooling system and as a heat pump.

In order to operate the eCoo/Zeo in heat pump mode, the recooling circuit or hot water circuit and the chilled water circuit have to be exchanged externally. This can be achieved via three-way switching valves, depending on the installation. In this case, either the recooler or the collector field are applied as a low-temperature source, and, for example, a cooling ceiling or a floor heating system are used for a heat emission into the room.

However, there are some limitations. The low-temperature source should not be colder than 10 °C, and the maximum supply temperature is 35 °C.

When the adsorption chiller is switched on for the first time, an initial start-up time of up to 15 minutes has to be taken into account, since it must run a complete desorption prior to the first adsorption phase (and thus cooling). Depending on the temperature level in the chilled water cycle at the outset, a certain time is required to reach the desired chilled water temperature. This also means that power cycling the chiller is generally not energetically efficient.

eCoo/Zeo chillers are connected to three temperature circuits – the hot water (drive) circuit HT, the recooling circuit MT as well as the chilled water circuit LT. What is the effect of different temperatures in these circuits on the performance of the chiller?

The relationship between the temperatures of these three circuits and the cooling power respectively the COP is best represented by the performance charts provided.

Generally speaking:

  • Higher drive temperatures increase the cooling power;
  • Higher chilled water temperatures increase the cooling power and improve the COP;
  • Lower recooling temperatures increase the cooling power and improve the COP.

The core of both technologies is a material which adsorbs water vapor (the adsorbent). Fahrenheit uses either silica gel, which has a very flexible drive temperature range, or zeolite crystals which, depending on their type, are particularly suitable for special conditions, e.g. hot climate zones, compact applications, or low drive temperatures.

In the eCoo adsorption chillers, silica gel is used as an adsorbent, while in the Zeo adsorption chillers, the adsorbent is zeolite.

(See also the questions about adsorption materials further up.)

Basically, the realm of potential adsorption applications is almost unlimited. An adsorption system is economically viable as long as excess heat is available.

Please find more information about common adsorption cooling applications here.

Yes, we continuously develop and evolve our products. Improving the performance and efficiency, reducing cost, volume, and weight, as well as broadening the fields of application are among of our developed goals.


Fahrenheit eCoo/Zeo adsorption chillers basically consist of these components:

  • One or multiple pairs of processing modules
  • Silica gel or zeolite coated adsorber heat exchangers
  • Switching unit incl. high-efficiency pumps
  • Controller and measurement system
  • Frame or supporting structure with cladding

The cooling module itself is resistant to corrosion since no oxygen is contained in the system, and it consists of materials such as stainless steel and copper. The supporting structure as well as the frame are generally protected against corrosion by surface coating, sufficient for a typical interior setting. If the chiller is to be permanently exposed to higher humidity, however, a special anti-corrosion coating may be needed.

There is no degradation or erosion whatsoever. The process of adsorption is completely reversible.

No, there isn’t. Fahrenheit mainly uses steel, copper, and aluminum in our products. Moreover, silica gel and zeolite are naturally occurring materials which are completely harmless. The chillers can be disposed of normally after the end of the service life.

The HybridChiller, such as the eCoo 10 HC 30, combines adsorption and compression cooling. It blends the environmentally friendly and energy efficient adsorption technology with the precision and power of compression.

In the HybridChiller, the adsorption part covers the main cooling load, while the compression part is engaged whenever a higher cooling load is required, or when there are fluctuations in the heat supply for the adsorption system. The combination results in maximum energy efficiency.

Yes, all our adsorption chillers can be combined with compression chillers.


In contrast to conventional air conditioning units, Fahrenheit adsorption chillers utilize heat in form of hot water as a drive source instead of electricity. As a result, the cost-effective thermal energy can be re-used, while otherwise this energy would be released into the outside environment, or re-cooled expensively.

eCoo/Zeo save primary energy and achieve greater independence from increasing electricity prices and power grid bottlenecks. Thus, they enable environmentally friendly and resource-saving cooling.

From the point of view of energy consumption, the most sensible heat source for an adsorption chiller is waste heat. If the waste heat required for operation is insufficient, compression technology can be used. This is possible by using the Fahrenheit Fahrenheit-HybridChiller, or a separately installed compression chiller. Using such a combination, fluctuations in the supply of waste heat can be resolved and peak loads are efficiently covered by compression.

In theory, adsorption chillers can also be driven directly, for example with a boiler. However, this is inefficient from an energy point of view and often does not pay off from an economic point of view. Such configurations should only be used in exceptional cases.

The drive temperature limit is primarily designed to accommodate the temperature tolerances of individual materials in the chiller. However, some safety margins are factored in, so that in principle a short-term overrun of the maximum temperature is harmless.

Excessively high drive temperatures must be prevented by external measures, for example by the return admixture, which is a common technique in heating technology.

Even at drive temperatures (HT) below 55 °C, cold is still “generated”, which means the chiller does not switch off automatically. This has the benefit of compensating short-term drops in temperature in the interest of continuous cold generation and to avoid power cycling. However, this situation is not desirable for continuous operation, since the demand for electrical energy (for example, for re-cooling) still exists at lower refrigeration capacity. A limitation of the drive temperature “downwards” can be achieved, e. g., via an optional hot water buffer tank sensor.
Even at drive temperatures (HT) below 55 °C, cold is still “generated”, which means the chiller does not switch off automatically. This has the benefit of compensating short-term drops in temperature in the interest of continuous cold generation and to avoid power cycling. However, this situation is not desirable for continuous operation, since the demand for electrical energy (for example, for re-cooling) still exists at lower refrigeration capacity. A limitation of the drive temperature “downwards” can be achieved, e. g., via an optional hot water buffer tank sensor.


Like all thermally driven refrigeration systems, the eCoo/Zeo also relies on recooling both the supplied drive energy and the produced/removed cooling energy. The recooling ensures that the energy adsorbed (during evaporation and desorption) can be released back into the environment. If the recooling temperature increases, the performance of the chiller generally decreases.

The thermal recooling energy can also be utilized sensibly (for example for drying processes, swimming pool heating etc.). In such setups, the overall efficiency is particularly high.

For our refrigeration systems, we offer as an optimally designed recooler with EC fans and optional fresh water spraying. This recooler adjusts its recooling capacity to the current load and thereby saves electrical energy. With the optional fresh water spraying, the amount of water is limited and only sprayed above definable outside temperatures.

In addition, wet cooling towers, geothermal probes, sea heat exchangers, wells, rivers, swimming pools or other heat sinks can be used for recooling.

The recoolers offered by us can always be used when outside temperatures are moderate and other outside temperature-independent heat sinks are not available.

Since ground probes or sea heat exchangers cannot be applied everywhere, other recooling variants should be included depending on the application and location. In particular, the integration of a wet cooling tower can be a sensible solution at high outside temperatures.

The rotational speed of the recooler ventilators as well as the optional spraying are controlled by the controller of the chiller according to the current operating state.
In order to conserve water and to avoid any deposits on the recooler heat exchanger, the spraying of the recooler is limited to those 400 hours with the expected hottest outside temperature. This corresponds to 4 m³ per year of water. If a smaller amount of water is to be used for recooling purposes, the number of spraying hours can be reduced. Increasing the number of spraying hours beyond the 400 h/a requires appropriate water treatment to improve its quality.
No, there isn’t. Compared to wet cooling towers, where circulating water may be contaminated, in the sprayed recooler a very small amount of water is injected into the airflow for a limited time. Any moistened lamellae will dry completely during the cycle. Moreover, a special “legionella circuit” is implemented into the controller so that any water remaining in the recooler’s supply lines is removed daily.
EC stands for electronically commutated. In comparison to the conventional AC fans, EC fans are continuously adjustable without additional equipment and have a lower power consumption, especially under partial load.
For this, frost protection measures must be taken. If the recooler is used as a low-temperature source for the heat pump in winter, it should be ensured that the hydraulics are protected against frost. In this case we recommend operating the recooler together with the Fahrenheit system separation with a water-glycol mixture (in Germany 34 %) that corresponds to the respective location.
The resource consumption depends on the power load. Due to the water spraying limitation, the consumption of water is limited to 4 m³ per year. The maximum power consumption of the recooler is specified in the technical datasheet. When properly installed, the eCoo/Zeo and eRec subsystem yield an annual performance factor of 10-14: Therefore, 1 kW of electrical energy serves to generate up to 14 kW of cold.


If the required cooling capacity drops below the minimum partial load range of the eCoo/Zeo (usually 60 % of the maximum cooling capacity), the cold carrier (brine) is gradually depleted of energy so that it cools down to the set frost protection limit (default: 4 °C). The system is then switched off. If a decrease to such low temperatures is undesirable, this can be modified by raising the frost protection limit (Controller Parameter T_Freeze). This should be taken into account especially in case of cold distribution systems such as cooling ceilings, where the dew point temperature should not be underrun.

The size of the room to be cooled is not sufficient to estimate the cooling load. The cooling load depends on the insulation standard, windows sizes, and internal thermal sources such as computers, lights, and people.

We recommend to perform an accurate calculation of the required cooling load to properly match the eCoo/Zeo with the cooling load.

The eCoo/Zeo cools a constant chilled water volume flow (cold carrier) which cools the ambient air when passing through chilled water-air-heat exchangers (such as ceiling cassettes or fan coils).

In particular, we recommend cold distribution systems which can operate on relatively high cold water temperatures, such as:

  • Floor cooling
  • wall cooling
  • Chilled ceilings
  • Cooling compartments
  • Concrete core temperature control
  • Circulating air coolers, air distribution systems

The combination of an eCoo/Zeo and CHP can be a very useful setup, which also benefits from increasing the CHP’s operating hours. The available HT temperature level (drive temperature) of a CHP is generally sufficient. In contrast to solar cooling, cold production is possible around the clock. Particularly for CHPs, the maximum HT return temperature should not be higher than a certain threshold. In order to compensate for fluctuating and temporarily higher than required HT return temperatures, we recommend installing a buffer downstream from the eCoo/Zeo. With a buffer volume of just 120 L, the fluctuations are reduced to a minimum.

A certain distance between the chiller and the recooler is necessary because the recooler has to be installed outdoors while the chiller is ideally installed inside the building. Long pipes result in greater pressure losses, which in turn requires higher pump performance. Therefore, the pipe diameters must be checked for long lines and adjusted if necessary.

Regarding the distance to the heat source, heat losses increase with distance, and therefore eCoo/Zeo should be located as close as possible to the heat source. In addition, the chiller should be installed in the immediate vicinity of the cold distribution network in order to prevent unwanted warming of the chilled water.


At higher outside temperatures, the advantages of the Zeo systems come into play. Higher ambient temperatures are easily tolerated.
When using the eCoo/eRec subsystem, the outside temperature determines the system’s economic viability, since COP drops at very high recooling temperatures (depending on LT and HT). Where exactly the application limit is depends on several parameters, such as the relative humidity. The lower the humidity, the higher the maximum outside temperature can be for the chiller operation. Higher ambient temperatures can also be compensated by higher cold water and/or drive temperatures. Generally, in the case of very high outside temperatures (>37 °C) in conjunction with high air humidity, more climate independent recooling options should be selected: For example, swimming pool heating, geothermal probes, sea heat-exchangers, or similar. At high outside temperatures and low humidity, a wet cooling tower can be the most efficient solution.
We will gladly prepare for you a design that is precisely tailored to the potential location and the expected operating conditions, including a proposal for the optimal recooling solution

A chilled water buffer tank is not necessary. Due to the slight fluctuation of the discharge temperatures of the chillers, a buffer can be used to smoothen the operation, as well as to simplify the integration of the eCoo/Zeo. It is also possible to use a buffer tank at night, for example, when the sun no longer provides the operating power for a solar-driven eCoo/Zeo.

A solar collector has an efficiency of up to 0.75, and our chillers of up to 0.6. Thus, up to 45 % of solar energy is used for cooling. In terms of electrical power consumption, the achievable efficiency factor is at least 14. Therefore, 1 kilowatt of electricity can generate about 14 kilowatts of cold, with the rest of the energy coming from solar thermal energy.


Since there are no movable parts within the eCoo/Zeo, apart from the 3-way switching valves and pumps, maintenance is not strictly required. Nevertheless, we recommend an annual system check of the integrated components and materials.

The inspection is carried out either by FAHRENHEIT or by trained and certified Fahrenheit partners.

With careful planning and design, the FAHRENHEIT adsorption cooling systems consume up to five times less electricity than conventional air-conditioning systems.

The eCoo/Zeo is switched on either manually via the input panel of the controller or, if provided, by activating the potential-free contact via an external control. All pumps and the recooler are automatically switched on by the eCoo/Zeo.

Once switched on, power cycling the chiller should be avoided. Every switching causes energy losses, however it has no negative effect on the eCoo/Zeo.

Adsorption chiller:

Dry, preferably at constant temperatures between +5 and 45 °C; avoid freezing


No restrictions as long as the hydraulics are drained

The system is stable within its specified operating conditions. Special measures to enhance the service life are not necessary.


Here you will find data sheets, installation and operating manuals, and additional information for your FAHRENHEIT product.

File Name
GOM – General Operating Manual